Sendmail

How to create .cf file from .mc

Rebuild aliases

when you modify /etc/mail/aliases.
Possibly you see following message. alias database /etc/mail/aliases.db out of date

Simply run following and will fix it.

newaliases

OR
run 'make' in /etc/mail to update all databases
OR

sendmail-bi

Error Code 126

Following messages you see in log and mail.

DSN: unknown mailer error 126

stat=unknown mailer error 126

runscript.sh: Permission denied

554 5.3.0 unknown mailer error 126

It is because script you call to catch email OR execute when received has permission issue.
Simply set permission on that script to “Sendmail Default User” could be 'daemon' or 'mailnull'.
the names i have used those are i came across till now. so chances are there you see something diff.